This invention relates to a track displacement detecting and measuring system.
In the New Tokaido Line of Japanese National Railways, track displacement has been measured by a track inspection car as disclosed in the References Nos. 1, 2, 3, 4 and 5. In the prior art track displacement detecting and measuring system of the type used in such a track inspection car, track displacement has been measured in a manner as described below. In this specification, the term "track displacement" is limitatively used to designate horizontal track displacement and vertical track displacement. The horizontal track displacement refers to horizontal deviation of the rails from a predetermined preset position in the direction perpendicular to the rail direction on the plane of the track, and the vertical track displacement refers to upward or downward deviation of the rails from a preset position in a vertical plane (referred to hereinafter as a longitudinal plane) along the extending direction of the track.
In the prior art track displacement detecting and measuring system, a sensor is mounted on each of a front truck, a middle truck and a rear truck of the track inspection car to measure deviation of the rails from a preset position in the transverse or vertical direction. The distance between the sensors mounted on the front and rear trucks of the track inspection car is set at a basic length for track displacement measurement (which length corresponds to a chord when a portion of the track is regarded as an arc), and the so-called three-point measuring method is resorted to for detecting track displacement on the basis of data obtained from the three sensors. This basic length is generally selected to be 10 meters in the case of the track inspection car above described. Thus, track displacement ranging over a track distance beyond this basic length cannot be correctly measured since the basic length is limited to 10 meters.
In a high-speed railway such as the New Tokaido Line of Japanese National Railways in which a train of passenger cars are designed to run at a maximum speed exceeding 200 kilometers per hour, the importance of proper track maintenance is greater than other railways of lower speeds in order to ensure the safety of train operation and to provide a comfortable sense of ride for the passengers. For example, according to the results of researches on the relation between track displacement and joggling of passenger cars, it has been found that horizontal track displacement and vertical track displacement ranging over a track distance of from more than about 10 meters to several tens of meters provide the greatest factor which causes joggling of passenger cars resulting in an uncomfortable sense of ride for the passengers. With such track displacement ranging over a long distance of the track (called long-wavelength track displacement by the parties concerned), not only the errors of measurement tend to increase inevitably, but also the desired measurement is rendered almost impossible when the so-called three-point measuring method based on the conventional basic length is resorted to.
For purposes of better track maintenance to ensure the safety of train operation, to provide the comfortable sense of ride for passengers and to permit running of the train at high speeds, a track displacement detecting and measuring system capable of precisely and conveniently measuring the long-wavelength track displacement has been strongly demanded.
In a system of this kind, a gyro device is generally used for the detection of vertical track displacement. The prior art system using a simple vertical gyro having two free axes has been able to measure the long-wavelength vertical track displacement only with difficulty due to the fact that such a gyro operates instably against rolling or joggling of the track inspection car to the left and right and is thus unable to ensure measurement with high precision.
According to the present invention which will be described in detail later, data obtained from sensors adapted for three-point measurement are ingeniously computed and processed while employing a basic length (a unit chord length) equivalent to that employed heretofore in the track inspection car, so that the result of the measurement (the detected amount of track displacement) is substantially the same as that obtained by a track displacement car having, as it were, a basic length which is two or four times the conventionally employed basic length. Further, according to the present invention, an improved gyro device capable of detecting vertical track displacement relative to the ground line is used so that long-wavelength vertical track displacement can be theoretically measured irrespective of the length of the track having such track displacement.
The measured data of track displacement must be recorded in exact coincidence with the measured points or positions. In a prior art manner of recording, the measured data is recorded, together with distance pulses occurring at intervals of a predetermined distance, on a recording sheet continuously fed at a rate proportional to the traveling speed of the track inspection car. However, the distance pulses are not always generated at a rate proportional to the traveling distance of the track inspection car, and the error due to lack of correspondence tends to accumulate to provide a large error which is no longer negligible in the measurement which is continued over a long distance. The prior art manner of recording has thus had a serious defect that the data obtained by the measurement is no longer relevant in an extreme case. In an effort to obviate such a defect, an optical position detecting device including reflecting members disposed along the track at intervals of a predetermined distance of, for example, 1 kilometer has been proposed. In the proposed device, an optical detecting means responds to the light reflected from the reflecting members to produce a detected position signal which is used for the correction of the error occurring in each of the sections of predetermined distance thereby avoiding accumulation of the error. However, this optical detecting means has had a low detection sensitivity and thus has not been fit for practical use.
The track displacement detecting and measuring system according to the present invention includes an improved optical position detecting device so that the physical position of the track inspection car can be detected with high precision thereby permitting highly precise measurement of track displacement.